Latino children have the worst health care access of any US citizen children1, 2 Restrictive state immigration policies may further exacerbate disparities. Omnibus immigration policies seek to increase immigration enforcement, restrict undocumented immigrants' access to services, and create criminal penalties for undocumented immigration.3, 4 Although these policies had immediate, drastic effects on communities,5 little is known about their effects on health care access for Latino children. Qualitative studies 6-10 indicate that omnibus policies reduce Latino children's health care access, regardless of parents' immigration status. Findings from the few quantitative studies that exist are mixed, however, and these studies suffer from weak study designs and non-representative samples.6,8,9 No studies have examined which aspects of health care access are most affected, how long effects last, or whether effects vary by individual or community characteristics. This study hypothesizes that (1) omnibus immigration policies reduce health care access for U.S. citizen Latino children, with effects that decline but do not disappear over time; (2) effects are greater for children of immigrants than for children of US- born parents; and (3) living in a county with a high proportion of Latinos attenuates effects. This study will use a comparative interrupted time series (CITS) design to estimate the effects of omnibus immigration policies on health care access for US citizen children of Latino descent up to four years after policies were passed. CITS is the most rigorous designs for evaluating health policy effects when a randomized controlled trial is not feasible.11 Data will come from the National Health Interview Survey and will include over 98,000 citizen Latino children in all 50 states over 14 year (2001-2014). The outcome measures will include the following indicators of health care access: dental and medical insurance coverage, use of preventive care, unmet health care needs, and regular source of care. Models will estimate immediate and long-term effects of policy passage on health care access. Interaction terms will be added to the models to test whether effects are moderated by parents' immigration status or by county Latino population. If sample sizes permit, analyses will be stratified by Latino national origin subgroup. Findings will have important policy implications. State immigration policies drive and set the course of immigration policy discussions at the federal level, and many state-level policies are eventually replicated at the national level.12 In the face of mounting pressure for immigration reform, it is critical to understand how immigration policies affect citizen children-both to steer policy in ways that protect children and to inform public health efforts to alleviate effects.